The parent U.S. application Ser. No. 09/11 8,888 (hereafter the '888 application) filed by the present applicant discloses a method for testing the soil contamination by ejecting a circulation fluid in the soil, with a very small proportion of a tracer fluid. Fluid samples are simultaneously collected wherein contaminant fluid concentrations and tracer fluid concentrations are measured and used for computing the effective flow rate Q', in the affected soil volume. The tracer gas is used to circumvent the fact that the value of the affected soil volume is not known. With the effective flow rate Q', the generation rate G of the contaminants in the soil can be computed. With this method according to the '888 application, the use of a tracer gas is compulsory.
Also, according to the method described in the '888 application, the circulation fluid is ejected into the soil by the probe at a greater flow rate than the fluid intake flow rate. This results in a local increase of the quantity of fluid near the probe tip, which creates fluid pressure differentials in the soil. The contaminant fluids will consequently be prone to migrating in the soil according to fluid pressure gradients instead of migrating according to fluid concentration gradients.
U.S. Pat. No. 3,685,345 issued in 1972 to Harold L. Wise, commented in the Background of the Invention section of the '888 application, shows a soil sampling apparatus including an outlet tube and an inlet tube each having an opened lower extremity located near the bottom of a hole having been drilled in the ground. A circulation fluid is ejected from the outlet tube lower opening, and the circulation fluid mixed with a proportion of contaminants is collected by the inlet tube lower opening. However, in the Wise patent, the entire hole is not subjected to the circulation fluid, since the fluid ejection and collection both occur near the lower extremity of the hole. Thus, it is not possible with the method described in the Wise patent, to determine an approximate affected soil volume to be used to compute the generation rate of contaminants in the soil. In any event, the object of the Wise method is not to verify the contaminant generation rate, but to verify the concentration of the contaminant fluid.